Columbus contracted with Japanese Pen Maker Yamazaki to put together a rather small run of these pens made out of vintage Italian celluloid. The emerald green and the lapis blue are the most commonly encountered colors.

Here is a photo of one their nibs, a medium:

The vertically-striped blue and gold model is the most uncommon, with only a handful ever produced.

The pens Jack125 showed are all modern Columbus pens made in Japan. These were all made after Columbus was sold to Santara Group in 1992.

Your pen is very odd. The 29 was first introduced in 1941. The original version was a button-filler and had a metal cap on both ends meant for the military. The later mass market version only had a metal cap top. You cap is odd because it has a solid wide metal band and I've never seen a Columbus pen with that kind of cap band.

Eugenio Verga had patented a piston mechanism in 1938 but I don't know how widespread this was in the pen lines. In the late 40's and fifties, the piston fillers were much more common. I think the 100 series pens used the piston mechanism in early 1940's.

In 1941, the factory was destroyed in a bombing attack and Columbus had to relocate. It is possible this pen was made during this era where put toegther from what the new factory had on hand. This was common among many Italian pen manufacturers during the wartime era. Kind of a factory 'frankenpen'.